The knowledge on hitch articulation angle is very critical for controlling towing stability of a vehicle-trailer, as well as backing up. There have been many attempts in monitoring the angle using a non-contact means such as camera, ultra sound device, radar, and/or laser. Because hitch mechanisms are exposed to the harsh environments, the devices described above are not robust enough. Also, the aforementioned systems are either too expensive or technically cumbersome. For many contact type sensors, the major drawbacks are the effects of the unwanted trailer motions, such as roll and pitch. Furthermore, during acceleration and deceleration, a ball may slip in the hitch socket causing errors in the angle measurement.
The prior art systems which measure hitch angles often utilize the dynamic hitch angle values to regulate vehicle dynamics. All of these systems proposed some methods of sensing hitch angle as a part of trailer motion control algorithms, such as jackknifing sensing, vehicle-trailer stability control, backing-up process control. The devices disclosed, however, have either some limits or deficiencies, which cause them to be neither accurate nor robust enough in the harsh environments.